Gibson P90, not poted??????

[Satamax]

Hi everybody!, i have a pair of real gibson P90's in one of the guitars i built, love teh sound, but i have an isue, they're squealing at high gain. I mean is it possible that gibson didn't pot their pickups? Bought theses late 90.

Bye.

Max.

[David Schwab]

Gibson never wax potted their pickups. Some were epoxy potted, like the SuperHB, but they never used wax. I've had many humbuckers and P-90's from 60's and 70's Gibsons ... none of them were ever potted.

[Mark Hammer]

One of the difficulties with Gibson pickups is that, unlike the alnico magnets and flatwork of Fender pickups, the plastic bobbins do not take kindly to the sorts of temperatures accompanying potting.

On the other hand, potting does not HAVE to involve dipping an entire coil into a bath of molten wax. If you can remove the outside tape without damaging the coil (and that can be a big if, sometimes), it is possible to let the pickup coil sit with an exposed side pointing upwards and drip melted paraffin onto the coil surface so that it seeps in a bit. If you point a hair dryer at the wax you've dripped on, you can slow the cooling down enough to jiggle the coil and let the wax seep in a bit more. It will not soak all the way through the way it would with a paraffin bath, but just like imperfect hum-reduction *some* anti-microphonic treatment is better than none. I've "semi-potted" some pickups this way with reasonable success, though I have to say I've never tried them out 8ft away from a cranked 4 x 12 stack.

I also strongly encourage you to consider using teflon plumber's tape to wrap the coil before reapplying the original adhesive-covered tape to the pickup. The teflon tape is thin, cheap, just the right width, can be wrapped quite tightly and conforms well to the surface of the coil without use of any adhesive. Sometimes, tugging the tape will compact the coil a bit and reduce microphonics. It also provides a kind of protective layer so that the adhesive-backed tape can be removed and refastened without damage to the actual coil.

[Satamax]

Thanks a lot Guys!

Well, i need to pot i think, Mark, you mean that gibson plastic doesn't like temps of around 80 degrees? I can pot pretty easily as i have a vacuum pump. Nother quick question, i want to shield the pickuo, should i shield teh front too and have only teh poles sticking out, or should i leave the whole front open, so it doesn't change the sound?

Bye.

Max.

[Mark Hammer]

80 degrees is obviously not that drastic. My guess is that traditional wax-melting temperatures are higher than that, though, and perhaps high enough to at least warp bobbins a bit.

Note as well that Fender pickups come with polepieces already inserted, and nothing to screw in. I doubt that the task of screwing in the adjustable polepieces on a P-90 or half a HB would be that easy if the entire coil was dipped into a potting bath and wax went into the screw-holes. Not to mention the need to clean the excess wax off the bobbin surface.

So, it just seems there are a whole bunch of practical reasons why Gibson probably sidestepped potting.

[paulh]

Potting P-90's

I've done many Gibson Pick-ups with good results. You can get wax that melts at a low temperature (about 130F / 55C ) and is specifically made for candle molds so it will flow into all the crevices.

[David Schwab]

I have some Fender humbuckers that have been potted in wax, so I don't think the plastic bobbins are a problem. I think it's just something Gibson didn't do.

Duncan asked lover about wax potting:

SWD: How about the 4 brass screws? They were used to hold the bobbins in place and to eliminate vibrations?
Seth Lover: Yes, in other words everything has to fit tight together or if you have some possible movement of one part vs. another you can get a pickup like a microphone--the coils tend to move or vibrate a little, you can talk into it and hear it out of the amplifier.

SWD: Have you heard coils squeal when too close to an amp.
Seth Lover: Well the squealing part, that could be electrostatic couplings between the speaker. Sometimes on amplifiers they do not ground one side of the voice coil. When they do that, the voice coil acts like a little radiating antenna and you can get electrostatic coupling into your pickup that may cause a high pitched squealing and quite often we were able to cure that by grounding one side of the voice coil in the amplifier. make sure that one lug of the terminal was grounded to the frame of the speaker. As soon as we tied the frame of the speaker to ground, then that would tend to quiet down in most cases. Now you can still get close enough to them where you’ll even that won’t help you much. But then normally an acoustic electric guitar you’ll get plain acoustic feedback or sound from the speaker will cause a howl. It depends where your tone controls setting, to what frequency you are tending to accentuate as to what frequency you are going to hear where it feedback’s. It’s not a very high pitched note, it’s generally lower.

SWD: On occasion Fender had feedback problems with microphonics at high volumes and use a wax solution to keep the components from vibrating.
Seth Lover: When they assembled the humbucking pickups usually they had to clamp down unit tightly until they soldered it together. That would keep them good and tight. If they didn’t keep it tight you could get that same condition where maybe even the magnet might vibrate a little bit.

[Steve A.]

Gibson never wax potted their pickups. Some were epoxy potted, like the SuperHB, but they never used wax. I've had many humbuckers and P-90's from 60's and 70's Gibsons ... none of them were ever potted.

The Burstbucker Pro pickups are wax-potted. But I guess that is the exception and not the rule...

Steve Ahola

[David Schwab]

The Burstbucker Pro pickups are wax-potted. But I guess that is the exception and not the rule...

That's one of their newer models, right? I guess they decided potting was a good idea! How are their new pickups anyway? I haven't played any new Gibsons in a while.

EMG even pots their pickups... kind of surprising since they are encapsulated in epoxy.

[Satamax]

How are their new pickups anyway? I haven't played any new Gibsons in a while.

Thanks a lot for your replies guys.

David, the new gibson, well the mini HB on the neck of the nighthawks seemed nice, and a lot of people are raving about the gibson studio's pickups, the 490R and T, but they're rather old now, there's also the 498 which is suposed to be good.

Bye.

Max.

[Possum]

destroying P90s

If your P90s are 70s or older you will destroy the vintage value of them by potting them. Buy some other pickups if you like potting and put them in, if yours are old I'll take 'em off your hands :-)

[Possum]

ooops

I see they are late 90s, sure pot 'em. I really don't like the sound of potted P90s they sound sterile to me. You would probably do just as well to buy some Mighty Mites for cheap, they are potted, if you've never worked on pickups before its likely you'll destroy them trying to take the tape off or removing the base plate, you need a super delicate touch to do this.

[Spence]

Paraffin wax melts fairly easily. I set a temperature of 65 deg celcius. Some people add beeswax to paraffin wax to lower the melting point further.

I don't pot PAF replica pickups unless they are going in a semi-acoustic.

P90's are wonderful pickups, full of expression which can sometimes be completely killed by potting. The black scotch tape wrapped around the coil should contain unwanted coil vibration.

[Regis]

Hi Max,

I put a GFS P90 in my Garbagecaster, and while it sounded good it was microphonic as hell even tho it was potted. I discovered that if I grabbed the pickup cover when it was squealing the squeal would stop. It seemed the cover was vibrating causing microphonics.

I took it to a friend who knows about such things and he removed the cover, dripped some wax inside, and replaced it. The wax helped seal the cover to the pickup and the squeal was much reduced.

That idea about wrapping plumbers tape around the pickup sounds like a good idea, that might work too.

regis

[Zhangliqun]

One of the difficulties with Gibson pickups is that, unlike the alnico magnets and flatwork of Fender pickups, the plastic bobbins do not take kindly to the sorts of temperatures accompanying potting.

That's odd. I've rewound and potted a bunch of Gibson pu's and never had a problem with the plastic bobbins warping or melting or anything. Just gotta keep the temp at 145-150F.